TMPGEnc PLEASE HELP!!!

Alright so I downloaded the beta version TMPGEnc b12a and tried to use it on a 2007 movie. The movie is one file containing the video and audio. When I clicked browse and selected the file I got the message that the file either could not be found or wasn't supported. It is an .avi file. When I tried to open the same file with audio it worked. So how do I open the video file?

Note: I also tried this with a newer version of TMPGEnc and the same thing happened.